1. Technical Field
The present invention relates to a full reflectance spectrum of a surface obtainment method and an apparatus therefor with which a full reflectance spectrum of a surface can be obtained even when the spectral characteristic of the light source and the response characteristic of the camera are unknown.
2. Description of the Related Art
Generally, obtaining a full reflectance spectrum of a surface requires knowing the spectral characteristic of the light source and the response characteristic of the camera. Here, the spectral characteristic of the light source can be easily measured, for example by using a measurement equipment such as a spectroradiometer. In another example, the spectral characteristic of the light source may be indirectly measured if the reflection spectrum and the camera's response characteristic are known, but if the various known reflection spectra are not sufficient, it may be difficult to guarantee the accuracy of the outcome.
In the case of the camera's response characteristic, there is no method of direct measurement, and the response characteristic may be measured by using a large number of narrow band light sources or color filters or by using a reflection spectrum and a light source with known characteristics. With this method, however, it can be difficult to perform the measurement even in a well controlled environment, due to its sensitivity to external light sources, and it can also be difficult to provide accurate measurements, because some of the results may require interpolation if the light sources or filters either are not sufficiently narrow or are not continuous.
In particular, the response characteristic of a camera may also vary according to the type of the lens, due to the deterioration of the sensors, and according to temperature. As frequent re-measurements are inevitable according to various circumstances, there is no actual value that can serve as a standard, making it impossible to verify the results.